With the development of city is accelerated year by year，the mental health of migrant children received more and more extensive attention. In this study，we investigated 293 12-16 year old migrant children of a migrant school in Changping District of Beijing city through interviews and questionnaire survey and analyzed their mental health status and related factors. We found that nearly 16% lived in home place for more than 10 years；more than 90% children lived in different city with their parents；more than half children looked forward to continue living in the city in future；the overall level on social support was low；the overall level of mental toughness was low；the polarization was more obvious in group for SCL-90. We provided the corresponding suggestions on the prevention and intervention measures for the adverse psychological problems of migrant children from the policy level，family education and school education aspects.